This invention pertains to earth tunneling machines. Specifically, this invention relates to a hopper and hood combination for shield-type tunneling machines, and to shield-type tunneling machines employing the same.
Earth tunneling machines typically have a rotatable cutterhead attached to a cutterhead support. The cutterhead is commonly equipped with drag teeth and roller cutters and has apertures on its face. As the cutterhead rotates, the teeth loosen earth, which passes through the apertures into an interior earth collecting chamber of the cutterhead where an earth conveyor means removes the accumulated earth.
A problem exists when the tunneling machine moves through soft earth, known as flowing muck, because this muck floods the interior chamber of the cutterhead, making cutterhead rotation and forward movement difficult. Additionally, an excess of flowing muck entering and passing through the cutterhead can cause the face of the tunnel and the surrounding earth to collapse. It is thus necessary to control and limit the flow of the muck to the cutterhead interior chamber.
Proposed solutions to the problems associated with tunneling through flowing muck, once it is encountered, include the attachment of flow limiters to the cutterhead and the associated interior chamber. However, the tunneling machine must be retracted from the tunnel and partially disassembled in order to attach these muck flow limiters.
Another solution to flowing muck tunneling is disclosed in U.S. Pat. No. 4,732,427 issued to Lovat. In the Lovat tunneler, the cutterhead has a muck ring that receives loose earth from the cutterhead through pivotally movable, closable doors. Under flowing muck conditions, the doors seal the muck ring from the cutterhead in response to earth pressure changes within the cutterhead.
However, none of the devices currently known in the art limit muck flow during flowing muck tunneling with a hood apparatus that can also be employed as well to tunnel through hard earth, known as dry muck, by functioning as a hopper to channel earth to the earth conveyor. Additionally, none of the devices for the purpose currently employed discloses a dual position hopper/hood apparatus that is usable in both positions with minimal tunneling machine disassembly.